U.S. Navy Strike Warfare Office questions the Insensitive Munition policy

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As part of their FY-1990 support effort for the Navy’s Strike and Antisurface Warfare Master Plan, the Assistant Deputy Chief of Naval Operations (Naval Warfare) tasked the Center for Naval Analysis, CNA, to “examine how technology has affected the need for insensitive munitions for weapons under development”. The CNA was asked to address, among other things, the magnitude of the Navy munition sensitivity problem, the cost of the major aircraft carrier explosive incidents, and test results for the prospective new IM explosive fills for the advanced bomb family.

The CNA report was issued in March 1991.82 The study reviewed all aspects of the IM program. In the conclusions, however, it considered only cost and explosive energy rather than the total on-target performance of modern munitions. The conclusions were based, apparently, only on the saturation bombing techniques used by the U.S. in Southeast Asia in the late 1960’s and early 70’s. They did not consider the smart weapons that became available at the end of the Vietnam conflict. The report concluded that:

“A reasonable balance between insensitivity and lethality must be maintained. …There is little question that reducing the sensitivity of energetic materials will enhance ship survivability. Nevertheless, loss of explosive performance could require increased quantities of ordnance and/or numbers of sorties to accomplish operational objectives.”

Further, the report stated that:

“…SD {sympathetic detonation} events are unlikely if all other standards are met, making both fills [AFX-920 and PBXN-109] (sic.) likely candidates to replace H-6. Nevertheless, both fills are expensive alternatives, and only PBXN-109 provides the necessary operational capability. If cost were not a factor, PBXN-109 would be the most reasonable replacement for H-6. In a period of austere funding, however, cost becomes a much more important factor. Perhaps thermal coatings and safer design techniques for bombs with H-6 are sufficient for normal operations. Problems arise during abnormal situations.”

The CNA report did not consider that the cost of the explosive in modern weapons was often insignificant compared to the total cost of the weapon system. The cost of the explosive material is a few hundred dollars. The cost of the weapon, however, is measured in the hundreds of thousands or even millions of dollars. The conclusions of the report continued by stating:

“History has vividly demonstrated the need for safety in naval operations. It has been projected that in four aircraft carrier fires alone, an estimated 148 deaths, 577 injuries, and $1.15 billion in FY 1991 dollars [sic] in ship and aircraft damages would have been saved had IM standards been in effect.

…. No attempt has been made to forecast the expected losses in future explosive incidents. However, the four aircraft carrier incidents since 1967 have been examined in detail. IM standards are estimated to significantly influence the magnitude of the damage, in terms of lives and material. For these specific incidents, IM standards would have reduced material loss 84% and lives 67%.”

In my view, even if we neglect the tragic lost of lives, the estimated 1.15 billion dollar material cost of the carrier incidents overshadows, by far, the cost of loading the new PBX compositions in munitions to avoid such disasters in the future. The cost factor invoked by CNA reminded me of a memorandum I found in the NAVSEA files written before World War I. In essence, the memo stated that TNT would never be used in large quantities and it would never replace Black Powder because it was too expensive and too difficult to make.

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82Center for Naval Analysis, A Historical Perspective of Insensitive Munitions and Their Estimated Contribution to CV Safety, John R. Tindle, Cdr., USN, CRM 90-260/March 1991.